Tube bending machine having pressure and back up rams



May 19, 1959 w. P. HILL 2,387,144

TUBE BENDING MACHINE HAVING PRESSUREAND BACK UP RAMS Filed May 19, 19552 Sheets- Sheet 1 INVENTOR JLM/Qfi W ATTORNEY y 1959 w. P. HILL2,887,144 I TUBE BENDING MACHINE HAVING PRESSURE AND BACK UP RAMS FiledMay 19, 1955 2 Sheets-Sheet 2 EL JE...

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ATTORNEY United States Patent TUBE BENDING MACHINE HAVING PRESSURE ANDBACK UP RAMS Walter P. Hill, Detroit, Mich, assignor to AeroquipCorporation, Jackson, Mich., a corporation of Michigan Application May19, 1955, Serial No. 509,558

1 Claim. (Cl. 153-48) This invention relates to a tube bending machineby which a straight tube section of bendable metal, such as aluminum,copper, or steel, is capable of being bent to have a smooth curved bendwithout collapse of the metal of the tube, or change in the wallthickness, whereby the initial interior and exterior tube diameters areclosely maintained.

It is an object of the invention to provide a machine by which straighttube sections can be cold formed accurately into curved tube bends orelbows in an economical and eflicient manner.

A further object of the invention is to provide a machine by which tubesections can be cold formed into accurate curved bends or elbows withthe use of standard lubricants which can be readily removed and will nothave any deleterious effect uponthe tubes, such as occurs with the useof graphite in a known machine for forming tube bends with the use of ahot process.

The above, and further objects and advantages of the invention residingin the construction, operation and combination of parts will appearclear from consideration of the following description With reference tothe drawings and from the appended claims.

In the drawings:

Fig. 1 is a plan view of a machine embodying the invention looking uponthe bottom die structure, the upper die structure being broken away,

Fig. 2 is a side elevation of the machine, with the upper die inelevated position,

Fig, 3 is a vertically exploded elevation view of the upper and lowerdies, on an enlarged scale compared with Figs. 1 and 2,

Fig. 4 is a perspective plan view of the lower die, with a filled tubein position for bending,

Fig. 5 is a detail view, showing a filled tube section in operativerelation to the pressure plunger, and

Fig. 6 illustrates a completed tube bend, or elbow.

In the drawings, 10 indicates the base casing of the tube bendingmachine upon which casing there is mounted a bottom die pad 12 carryinga bottom die 14 having a U-shape groove 16 of semi-circular crosssection.

Mounted for vertical reciprocation above the die 14 there is an upperdie 18, carried by a die pad 20 and having a U-shape groove 22complementary to the aforesaid groove 16.

The upper die pad 20 is secured to a plate 24 mounted, as by theadjustable nuts 26, upon vertical posts 28 connested, in turn, to alower plate 30 carried by the piston rod 32 of a hydraulic piston andcylinder assembly 34 which is operable to move the upper die 18 upwardlyand downwardly with respect to the lower die 14.

The upper and lower dies are mounted upon their respective die pads sothat their U-shape grooves lie exactly opposite one another, wherebywhen the upper die 18 is closed upon the lower die 14 the grooves 16 and22 combine to form an enclosed tubular U of circular cross section.

2,887,144 Patented May 19, 1959 Vertical posts 36, secured to the upperdie, engage in aligned bores in the upper die and serve to form guideposts. Slots 38 in the surfaces of the dies presented to theirrespective die pads form key guides by which the dies are accuratelyalignable to position their U-shape grooves in exact opposition.

In their fully closed position the mated die grooves are completelyclosed except at the outer ends of the legs of the U, where, as seenclearly in Figs. 1 and 4, a

pressure ram 40 is positioned in one leg 42 and a back-up pressure ram44 is positioned in the other leg 46.

Pressure ram 40 is connected with a hydraulic piston and cylinderassembly 48 so as to be reciprocable with respect to the leg 42, whileback-up pressure ram 44 is connected for likewise operation by ahydraulic piston and cylinder assembly 50. Tie bars 52 (Fig. 1) connectthe assembly 50 to actuate the back-up ram 44, this ram being secured toa plate 34 to which the said tie rods are secured and which plateoperates in a guide 56.

Mounted within the U-shape groove 16 of the lower die are a series ofhard ball elements 58 which, in operation, form, in chest a flexibleextension of the back-up ram and lie in tandem arrangement between apressure pad 60 at the inner end of the ram 44 and the inner end of thetubular workpiece 62 to be operated upon. These ball elements arecapable of moving along the curved bend 64 of the U-sl1ape die groove,in advance of the workpiece, as will be understood.

To prepare the workpiece 62 for operation upon for bending to the shapeof the U-shape die groove the workpiece is filled with a suitablefiller, indicated at 66 in Fig. 5, which fillerwill hold the tubularworkpiece against collapse and will preclude any appreciable thinning ofthe workpiece wall. A suitable filler is a lead alloy material knownunder the registered trademark Cerrobase. The material should be capableof being filled into the tubular workpiece and of being readilyremovable, as by melting, in which case the heat necessary will be suchas will not adversely affect the workpiece. The filler materialspecified fulfills the requirements. It is malleable, inert to suchmaterial as aluminum, steel, and copper and has a relatively low meltingpoint.

The pressure ram is shown fitted with a cylindrical pad of an externaldiameter and thickness equivalent to that of the workpiece, whereas theram itself is of a diameter, as seen particularly in Fig. 5, that itpresents an inner end portion 70 which is capable of contacting one endof the filler 66 in entering relation to the tube 62, with the padhaving reciprocable guiding relation to the groove leg 42.

In operation, with the upper die 18 held raised, a tubular workpiecefilled with a filler, as seen in Fig. 5, is inserted in the leg 42 ofthe lower die, the pressure ram 40 being in retracted position and theback-up ram 44 being in projected position, all as seen in Fig. 4. Withthe inner end of the workpiece constituting a leading end and theopposite end constituting a trailing end.

With the parts positioned as seen in Fig. 4, lubricant is applied to theexterior surface of the workpiece and the upper die 18 is closed uponthe lower die by actuation of the piston and cylinder assembly 34.Pressure is then applied to the pressure ram 40 to force the pad 68against the adjacent end of the workpiece 62, as described withreference to Fig. 5, at the same time as the ram end portion 70 exertspressure against the corresponding end of the filler 66. At the sametime, back-up ram 44 exerts an opposing pressure, through operation ofthe piston and cylinder assembly 50, against the ball assembly 58 andthis, by the partial entry of the ball 58 into the corresponding end ofthe workpiece will exert pressure against the filler 66 and the adjacenttube end in opposition to the pressure exerted by the pressure ramportion 70 and the pad 68.

The pressure exerted by back-up ram 44 is capable of being over-ridden,as by the provision of a suitable relief valve (not shown) in thehydraulic system, by the pressure exerted by the pressure ram 40. I Thisram, therefore, will operate to push the workpiece 62 forward and aroundthe bend of the closed die groove, with attendant bending of theworkpiece to conform with the shape of the bend 64 and receding of theback-up ram. Upon completion of the bending operation the upper die israised and the bent workpiece removed from the lower die. The bent tubeis then cleaned to remove adherent lubricant and the filler removed,leaving the finished tube bend 72 as shown in Fig. 6. With the presentmachine, it is only necessary to employ standard lubricants, which canbe easily removed and leave a lubricant clean surface which will permitadequate braze penetration when, as is usual, the tube bends or elbowsare brazed to adjoining pipe or conduit ends.

I claim:

In a machine for forming tube bends up to 180 from tube sectionspre-filled with a malleable filler medium for holding the tube sectionsagainst collapse during bending, support structure, die structuredefining a tubular curved bend of 180, means mounting said die structurefor movement upon said support structure to open and close said tubularcurved die bend, said bend including-parallel straight end portions, apressure applying ram, a back-up pressure ram parallel to said pressureapplying ram, means mounting said pressure ram for reciprocation in oneof said straight end portions, means mounting said back-up pressure ramfor reciprocation in the other straight end portion, a plurality ofcontiguous ball elements of slightly less diameter than the bore of saidtubular curved die bend movable around and located within said die bend,said balls being sufiicient in number to extend the length of said diebend whereby balls will simultaneously be in alignment with both of saidstraight end portions, one of said balls engaging said back-up ramwhereby said plurality of balls form a flexible extension of saidback-up ram, said tubular die bend adapted to axially receive a filledtube section under opposed endwise pressure by said pressure ram andsaid back-up ram while situated endwise between the inner end of thepressure ram and the back-up ram extension means, said ball elementsexerting pressure against one end of the filled tube section and saidfiller medium in opposition to a greater pressure exerted against theopposite end of said tube section and said filler medium by saidpressure ram whereby said ball elements will move around said die bendas the pressure ram overcomes the pressure exerted by said back-up ram.

References Cited in the file of this patent UNITED STATES PATENTS1,429,924 Brinkman Sept. 26, 1922 1,560,201 Bingham Nov. 3, 19251,947,611 Miokte Feb. 20, 1934 2,334,661 Weimer Nov. 16, 1943 2,335,342Kvarnstrom Nov. 30, 1943 2,701,002 Arbogast Feb. 1, 1955 FOREIGN PATENTS472,790 Canada Apr. 10, 1951

